The invention described herein is directed generally to comb filters and particularly to a filter and method for separating the luminance and chrominance components of a television signal encoded according to NTSC standards.
A Fourier analysis of the signal in the video domain indicates an energy spectrum concentrated in discrete clusters with interval spacings of line frequency (i.e. 15.734 kHz) with subside bands grouped around each 15.734 kHz interval at multiples of 60 Hz and 30 Hz spacing. According to the NTSC standard the color subcarrier and its modulation side bands are interleaved with the base band spectrum by synchronizing the subcarrier with horizontal sync as an odd multiple of one half line rate.
This interleaving enables the separation of the luminance and the chrominance signal by comb filters. Examples of such filters are described in RCA Review, March 1980, Vol. 41, No. 1, pages 3 to 28.